Intermittent inductive train control



C. S. BUSHNELL INTERMITTENT INDUCTIVE TRAIN CONTROL Filed April 16, 1925 2 Sheets-Sheet 1 Get, 2, H928. 1,685,434

c. s. BUSHNELL INTERMITTENT INDUCTIVE TRAIN CONTROL Filed April 16, 1925 2 Sheets-Sheet FIG. 4.

Patented Oct. 2, I928.

, U N l T ED T CHARLES S. BUSHNELL, OF ROCHESTER, NEW YORK, ASSIGNOR TO GENERAL RAIL- WAY SIGNAL. COMPANY, OF ROCHESTER, NEW YORK.

INTERMITTENT INDUCTIVE TRAIN CONTROL.

Application filed April 1 6,

type.

In a certain well recognized tramcontrol system Control. influences are transmitted from the trackway to suitable car-carried apparatus from suitable inert trackway devices governed in accordance with traflic con ditions ahead. Generally speaking, the principle of transmitting control influences by this system consists in diverting flux through an influence receiving coil under danger traffic conditions by the action of an unmagnetized or inert body of magnetic material along the trackway which is ineffective to transmit such control influence when a coil surrounding said body is closed in a circuit of low resistance. An influence co'mmunicatingmeans of this kind has certain desirable features, the principal one of which is that no trackway energy of'any kind is required. Another advantage experienced in this system is that the rate of diversion or change of flux in the car-carried influence receiving coil and in turn the voltage induced in said coil by such change of flux increases with the speed of the train so that suitable electro-responsive devices may be operated bysuch influence at extremely high speeds as well as at the lower speeds, in spite of the fact that the time during which influences may be communicated decreases as the speed increases. Obviously, in a system of this kind an influence cannot be communicated while the car-carried device is moving over a trackway device at an extremely low speed, this because a certain rate of movement is necessary to effect the necessary rate of diversion of flux; also, a certain limit of sensitiveness of the car-carried apparatus is necessary, so that the car-carried apparatus does not respond when it moves by a trackway device which has its coil closed in a circuit of low resistance, and since the sensitiveness of the car-carried apparatus heretofore proposed is not the same for all conditions, this varying with the voltage of the battery used in connection with the car-carried apparatus, the outside temperature, and the like, it is proposed in accordance with the present invention to provide a current regulating device or ballast lamp which regulates the flow of current to the car-carried apparatus, so to speak, regardless of certain variation in battery voltage and variations in the resistance of the various circuits due to temperature changes,-

1925. Serial No. 23,572.

so that the car-carried apparatus may be designed to Work properly from extremely low speeds and up to extremely high speeds, operation at speeds of 90 miles per hour having been obtained.

Other objects and purposes of the present invention reside in the provision of a system including suitable manually operable acknowledging means whereby the engineers vigilance may be manifested and suitable manually operable reset means.

Other objects, purposesand characteristic features of the invention will appear as the description progresses.

In describing the invention in detail, reference will be made to the accompanying drawings, in which Fig. 1 illustrates conventionally and in a diagrammatic manner a very simple type of railway block signaling system upon which the trackway apparatus of anembodimcnt of the present invention is superimposed;

Fig. 2 shows diagrammatically the carcarricd apparatus in which the various devices are shown conventionally:together with a side elevation of a trackway device and the manner in which this device cooperates with the car-carried influence receiving element;

Fig. 8 shows the current regulating device or ballast lamp mentioned and Figs. 4 and- 5 show modified forms of th invention.

Track-way apparatus.Referring to Fig. 1 of the drawings, the reference character 1 designates track rails divided by insulating joints 2 into blocks, the block I and the adjacent ends of two other blocks H and J being shown. Since the various blocks are the same, like parts of each block are designated by like reference characters having distinctive exponents.

A In the particular arrangement shown the entrance end, of the block I-is provided with the usual track relay 7, which under normal clear traffic conditions of this block is main tained energized by the usual track battery 3 through a circuit including the rails of the block I in series, thus constituting the usual closed track circuit. At the entrance end of the block I is also located a line relay 4 which under clear traflio conditions of the blocks I and J is maintained energized by a circuit including contact 5 of the track relay 7 and contact 6 of the track relay 7 The reference character B represents a terminal of a. v

suitable source of ener such as a battery having its other termina connected to a suitable common return wire 0. The present invention is preferably used in connection with wayside signals of any of the various Well known types, such as, color light or semaphore signals and for convenience semaphore signals Z only have been shown without illustrating their well known operating mechanism and control circuits. I The apparatus thus far described comprises that necessary for wayside signal control purposes; in addition to this apparatus there is provided a trackway influence communicating element or inductor '1 which comprises a U-shaped core 10 terminating in enlarged pole pieces 11 and having a coil 12 thereon which coil is normally closed in a circuit of low resistance by a front contact 13 of the line relay 4:. This track element '1 is preferably located on the right hand side of the track the normal direction of traflic being as indicated by the arrow, and has its pole pieces located a; few inches above the top of the rails, so that .this track element has an influence communicating advantage over that of other magnetic bodies along the track, such as diverging switch rails, crossing rails, and the like.

By looking at the trackway apparatus shown in Fig. 1, it is obvious that the coil 12 of the track element T is closed in 'a circut of low resistance when both the block at the entrance end to which it is placed and the block next in advance thereof are unoccupied, and that it is open-circuited, thereby causing the track element to assume its active condition,-when either of these blocks is occupied,. that is, is active under either caution.- or

the car-carried circuit arrangement and operered.

ating features of the system will be consid- The ear-carrie apparatus includes a control relay OR, a repeater relay RR and a brake control relay BRJ These relays are constructed so as to be immune to 'jars and vibration, quick acting and responsive to very slight changes in current flowing-in their windings.

This car-carried apparatus includes a suitable-electrically operated audible signal conveniently called a whistle value WV, and also 1 includes an electro-pneumatic valve EPV whichmay control a suitable pneumatically operated brake pipe venting device which if operated retards the movement of the train or the EPV may control a pneumatically operated brake valve actuator, as desired.

.This device EPV representing suitable means to effect an automatic brake application of any degree or character desired upon the deenergi zation of a circuit, this conventional representation is considered sufiicient since the resent invention is not directed to any partlcular type of brake control apparatus.

The car-carried influence receiving apparatus comprises an influence receiving element L including an inverted U-shaped core 16 of laminated magnetic material terminating in enlarged pole pieces 17 spaced to properly cooperate with the pole pieces 11 of the trackway or inductor element T. This core 16 is provided with a primary or flux producing coil P and a secondary \or influence receiving coil S. I

In previous influence communicating systems of the type to which the present invention is particularly directed, changes of battery voltage and changes in the resistance of the various devices due to changes in tempera.-

ture made it necessary to sacrifice sensltlveness of the car-carried apparatus in order to avoid the transmission of control influences when passing by inductors in their clear t-rafiic condition, that is, having their coils closed in a circuit of low resistance. In the present invention a current regulating device or ballast lamp BL is employed to com pensate for these variable factors.

This current regulating device or ballast lamp BL has been more clearly shown in Fig. 3 of the drawings, and comprises an evacuated sealed globe filled with nitrogen similar to that used in incandescent lamps in which a ballast unit 71 of resistance wire having an extremely high temperature coefiicient of resistance is contained; this ballast unit as it heats .up causes its resistance to rise very rapidly as compared with the resistance change in the rest of the circuit when the current is increased. On account of the construction of this lamp and also on account of the manner in which it is housed in practice, the unit 71 itself being not exposed to the outside temperature, if the current flowing therein decreases slightly for some reason or other, the temperature of this unit and its ohmic resistance drops, causing the current to again increase practically to its normal value. In other words the ballast lamp BL consists of a ballast unit contained in a vacuum or inert gas .so that very little heat radiation and no oxidization takes place and in which a change of temperature due to a change of currentflowing therem causes the resistance of this unit to change abruptly and in this way causes it to be self ad usting, and causes it to automatically regulate the flow of current in the circuit in which it is contained. This ballast lamp BL is provided with the usual lamp base :72 which in practice is screwed into a lamp socket of the usual construction. This ballast lamp is so located'in the circuit arrangement as to affect those circuits in which the degree of energization is very important. The main wire including this ballast lamp BL is included in the circuit containing the primary coil P and the brake control relay BB in series which circuit-may be traced as follows :beginning at the terminal B of a suitable source of energ wire 20, front contact 21, of the repeater relay RR, wires 22 and 23, front contact 24 of the brake control relay BR, wires 25, 26 and 27 winding of the brake control relay BR, wires 28 and 29, ballast lamp BL, wire 30, primary coil P back to the common return wire C connected to the other end of said source of energy. The provision of this ballast lamp BL, which is preferably so located as not to be affected by outside temperature, causes the current flowing in this circuit to be substantially constant regardless of ordinary variations in battery voltage and changes of the resistance of this circuit due to temperature changes, contact resistances and the like.

In order that the current flowing in the control relay CR, which relay is connected in series with the secondary winding S, may vary with the slight changes in the current in the primary coil P, the potential for supplying current to this control relay GR is the resistance drop across the brake control relay BR. In other words, the control relay CR and secondary coil S are connected in series with each other and in multiple with the brake control relay BR through the following circuit :beginning at one side of the winding of the brake control relay BR, wires 27 and 32, front contact 33 of the control relay CR, wires 34 and 35, secondary coil S of the car element L, wires 36 and 37, winding of the control relay CR, wires 31 and 28 back to the other terminal of the brake control relay BR. The various constants are. so chosen that the potential across this brake control relay BR is suflicient to hold the control relay CR energized to a predetermined degree just enough to keep this relay from dropping under most unfavorable conditions of battery voltage apd temperature, when traific conditions are c ear.

With the control relay CR energized the repeater relay BB is energized through the following circuit :-beginnin at the terminal B, wire 20, front contact 21 ofthe repeater relay RR, wires 22 and 23, front contact 24 of the brake control relay BR, wires 25,- 26 and 32, front contact 33 of the control relay CR,

wire 38, winding of the repeater relay RR, wire 39, back to the common return wire C. It is thus noted that the repeater relay RR is connected ir. astick circuit including its own front contact 21, and that this stick circuit also includes a front contact 33 of the control relay CR. It should also be noted, that the brake control, relay BR and the primary coil P which are connected in series include the front contact 24 of this brake controlling relayBR, so that this relay BR is also conneoted in a stick circuit and similarly, the control relay GR is connected in a stick circuit including its front contact 33.

With these relays energized an energizing circuit for the brake control device EPV is closed which may be traced as follows :beginning at the terminal B, wire 20, front contact 21 of the repeater relay RR, wires 22 and 23, front-contact 24 of the brake control relay BR, wires 25 and 40, front contact 41 of the reset push button PB,'wire 42, slow releasing contact 43 of the acknowledging push button Ack, wire 44, winding of the device EPV,.wire 45 back to common return wire G. The front contact 43 of theacknowledging device Ack is slow releasing because it is retarded by the dash pot 46, this dash pot being provided to permit the acknowledging push button Ack to be depressed for a predetermined period of time without opening the energizing circuit for the brake control device EPV.

Operation (Fig. 2).As heretofore mentioned, the present system is one of the permissive or semi-automatic type, that is, a

system in which an automatic brake application is initiated if the engineer fails to manifest his vigilance when passing an active control point, this being assumed to be suilicient to effect stoppage of the train when the engineer is dead, incapacitated or is not attending to his duties for any other reason.

In order to clearly understand the operation of the system, thetransmission of a control influence-when the engineer does not manifest his vigilance will first be taken up, after which it will be shown how the engineer can avoid an automatic brake application by depressing the acknowledging push button Aek 10$ at the time he is passing an active trackway inductor, and what takes place when aninactive inductor is passed.

Let us assume that a train equipped with the car-carried apparatus shown in Fig. 2 passes by an inductor having its coil-opencircuited because traflic conditions ahead are dangerous. -As the car-carried element L gets into communication with the trackway element T the reluctance of the magnetic circuit including the primary coil P and the secondary coil S materially decreases so that a rapid increase of flux through the secondary coil S takes place. This increase of flux, it is believed, is mainly due to a diversion of flux from leakage paths and, possibly to a certain extent, is due to an increase of the total flux passing through the primary coil P. This increase of flux through the secondary coil S induces a voltage in this coil 1 which voltage is in a" direction opposite'to that of the resistance drop due to the ener- .gizing current flowing through the brake in the current in the control relay GR is sufiicient to cause it to assume its retracted position'if the speed of the train is above a certainlow value, more particularly discussed hereinafter. .Momentary de-energization of the'control relay CR causes it to drop its front contact 33 thereby interrupting the energizing circuit for this relay so that this relay continues to assume its de-energized position. As the car-element recedes from the track element a voltage is induced in the coil S in the opposite direct-ion for obviousreasons, but this voltage has no effect because the stick circuit ,for the relay GR is open.

With the contact 33 in its retracted osition the repeater relayRR is de-energi'zed. With the repeater relay RR de-energized the energizing circuit for the brake control relay BR and the device EPV are broken so that these devices assume their de-energized positions and an automatic brake application, which brings the train to a stop; results. After the train has been brought to a stop by such a brake application the engineer, after; alighting from the cab, may restore the ap paratus to normal by depressing the reset r This circuit for pickingv up push button PB which is contained in a cas ing as shown by the dotted rectangle, and: is only accessible from the ground.

It now, the engineer depresses the push button PB a pick-up circuit for the brake control relay BB is closed as follows :beginning at the terminal B, wire 50, back contact 51 of the reset push button PB, wires 52, 40, 26 and 27, brake control relayBR, wires 28 and.29, ballast lamp BL, wire 30, primary coil P back to common return wire C. v Also, with this push button PB depressed a pickup circuit for the control relay OR is completed as follows :beginning at the terminal B, wire 50, back contact 51'of the ush button PB, wire 52, back contact 41-0 .the push button PB, wires 53 and 37, winding of the controlrelay CR, wires 31 and 29, ballast lamp BL, wire 30, primary coil P back to the common return wireC. With the control relay CR again picked up the repeater relay RR assumes its energized position for obvious reasons, and since the brake control relay BR is again energized its stick circuit .up thereby closing a shunt around the whistle is completed through contact 21 of the repeater relav RR so that all relays as well as the device EPV again assume their energized positions andpermit the train to proceed. the relay-RR comprises :-"-B, resistance contacts 24, wires 25, 26 and 32, contacts 33, wire 38, relay RR, wire 39, to common return wire Let us now assume that the train with its car-carried apparatus in its normal condition passes, by an active traokway inductor at a time when the engineer is vigilant and manifests his wakefulness by operating the l acknowledging push button Ack. With the acknowledging push button Ack depressed,

energized position upon completion of its potential is applied to the winding of the stick brake control relay BR and its stick contact 24 through the whistle valve WV, so that this brake control relay BR remains energized regardless of the de-energization of the control relay CR and the repeater relay RR. This artial circuit for the brake control relay R includes wire 56, winding of the whistle valveWV, wire 57, back contact 58 of the acknowledging push button Ack, wires 59 and 23. It should however be-noted that during acknowledgement (Ack depressed) and with'relayRR also .ener-. gized practically no current will flow through winding of'whistle valve WV, because it is shunted by the contact 21 of relay RR.

In any event the small current that may flow is insufficient to operate and sound the whistle valve WV. As an influence is received by the secondary coil S upon passage of the car element L by the tra'ckway inductor T, for reasons heretofore given, this control relay CR assumes its deenergized position and de-energizes the re peater relay RR. With the repeater relay RR in its de-energized position the brake control relay BR has its current fed through g the whistle valve WV, so that an audible signal is given so long as the repeater relay RR is 'de-ener ized, the, current flowing '9 through the whistle valve WV however, bemg suflicient to maintain the brake control re ay.BR and in turn the device EPV energized. With the repeater relay BB in its deenergized position a pick-up circuitifor the control relay OR is completed which may be traced as follows :-beginning at the terminal B of a suitable battery, wire 56, whistle valve WV, wire 57 ,back contact 58 of the acknowledging push button. Ack, wires 59 and 23, front contact 24 of the brake control relay BR, wires 25 and 60, back contacts 61 of the repeater relay RR, wire 62, back contact 63 of the acknowledging push button Ack, wires 64 and 35, secondary coil S, wires 36 and 37, winding of the control relay CR, wires 31 and 29, ballast lamp BL, wire 30, primary coil- P, back to the common return wire C, With the control relay, CR again picked up the repeater relay BB is picked valve WV, so that, the whistle is no longer sounded, and the stick circuit for the brake control relay BB is again completed and the engineer may release the acknowledging push button Ack, it being of course assumed that the .trackwaydevice has been passed over by this time. It is of course understood that the control relay would not have assumed its pick up circuit had there still been an appreciable voltage induced in the secondary coil S due to an increase of flux, but that it will pick up when the trackway device has been passed over. It should be noted that the 3 front contact 43 of the acknowledging push button Ack is not under Ordinary operating conditions allowed suflicient time to open and de-energize the valve EPV, the dash pot 46 being constructed to allow sufficient time for the engineer to manifest his vigilance, but.

so as not to permit the engineer to maliciously fasten down the acknowledging push button Ack and thereby defeat the purpose of the train control system. In this connection, it should also be noted that the reset push button PB is protected against misuse by the front contact 41. that is, this contact 41 de-energizes the EPV so long as the push button PB is-depressed; this is, however, not harmful because the push button PB is only required to be operated while the train isstanding still and if the device EPV is deenergized at this time no particular harm is done.

We have thus far in connection with the operation of the system considered the train passing an active inductor when no acknowledgment is made by the engineer, resulting in an automatic brake application, and have considered passing an inductor when such acknowledgment is made which results in an audible signal and no automatic brake application; The audible signal given in this way serves two important functions. In the first place the momentary sounding of the whistle informs the engineer that he has passed the active control point, and that he may new release the acknowledging push button Ack and thereby avoid an application by the eventual opening of the slow releasing contact 43 of this acknowledging device. In the second place, the soundingof the warning whistle informs the engineer that his train control apparatus works properly so that he may report accordingly at the end of his run.

Let us now consider what takes place when the carcarried apparatus passes an inactive inductor, that is, an inductor having its coil closed in a circuit of low resistance. As the car element L passes upon a trackway inductor having its coil in a closed circuit of low .resistance no rapid increase of flux through the secondary coil S takes place. This, it is believed, is due to the bucking action of the coil 12, that is, a slight increase of flux through the track element or inductor T causes an appreciable current to be set up in the closed circuited coil 12 which current is in a direction to oppose the flux producing it. This slight increase of fiux' through the track clement T allows a similar increase of flux through the secondary coil S, but this slight increase of flux through the secondary coil S is insufficient to induce the necessary voltage to de-energize the control relay OR. As the car element recedes from the track element T the flux passing through the secondary coil S again decreases without any matecharge resistance 7 3 and the front contact 24L of the relay BR. This resistance is employed to prevent excessive arcing at the contacts 21 when the relay RE is de-energized and does not allow the flow of sufficient current tomaintain the relay BR up, so that the dropping of its contact 24 completely de-energizes the'device EPV. In other words, the current for energizing the primary coil Pand the device EPV is out off in two steps, so to speak, that is, is first reduced and then entirely out off through the medium of contacts 21 and 24: and discharge resistance 73.

Let us now consider how the margins of operation of the present system have been improved over previous systems of the same general type by the addition of the ballast or regulating lamp BL. In previous systems it was necessary to keep-the current in the control relay at a higher margin above drop away, pr it was necessary to keep the current in the primary winding lower than is now necessary, this, in order to avoid the transmission of a control influence in passing over an inactive or closed circuited inductor under conditions when the current in the control relay is a trifle low, either because of an increase inthe resistance of the circuit or because of a decrease of the voltage of the source of supply for energizing this circuit. That is, in the present system by reason of the provision of the ballast lamp, which maintains substantially a constant flow of current in the primary coil P, the relays GB, RB and BB regardless of ordinary changes in temperature and battery voltages function properly and always the same, and-by the addition of this ballast resistance it has been possible to adjust the various currents so near their critical value that the system functions when the car-carried apparatus passes by an active open circuited inductor at extremely low speeds. Successful operation of the present system under most adverse conditions and changes of battery voltages and outside temperature has been obtained at all speeds between about one-half mile per hour and the highest speed obtainable by a locomotive,

whereas in previous systems it was necessary to adjust the currents in the various car-carried circuits to a value making the apparatus less sensitive so as to avoid false operation under adverse conditions of voltages and circuit resistances, and by such adjustment it was possible to transmit control influences lating device or ballast lamp BL and in those systems operation could'not be obtained below three miles per hour. This was true because the car-carried apparatus could not be adjusted extremely sensitively because if this were done it would respond when passing over a clear inductor at a time possibly when the battery voltage on the car was above the average or possibly because extremely cold weather existed and the resistance of the 'circuits were below the average value. By the employment of the ballast lamp BL it has been made possible to adjust the various constants of the car-carried apparatus, so that operation has been obtained from speeds of mile per hour up to said highest speed under all conditions of ordinary changes in battery potential, changes of temperature, contact resistances and the like. In other words, the provision of the ballast lamp BL has enabled the inherently changeable factors of the system to be made pracf ically con stant so that the operating margin of the system has been materially increased, that is,

the; minimum speed at which control influence's could ordinarily be transmitted has been reduced.

Structure (Fig. .4).-In Fig. 4 has been shown a modified form of the present invention in which a ballast lamp BL is used in series with the circuit including the primary coil P, but wherein the primary coil P is notdeenergized each time thatan auto atic brake application occurs. In the ar angement shown, a check relay CkR is employed instead of the brake control relay BR which is cdntained in a somewhat different circuit arrangement so that this check relay CkR is not automatically controlled at all, but merely serves to check the'presence of a predetermined amount of current flow in the primary coil P. In thiscircuit arrangement the circuit for energizing the primary coil P may be traced as follows :beginning at the terminal B of a battery, wires 80 and 81, winding. of the check relay CkR, wires 82 and 83, ballast lamp BL, wire 84, primary coil P, wire 85 back to common return wire 0 connected to the other terminal of such battery. With a flow of current in the circuit just traced, a potential drop exists across the check relay CkR which potential is used for energizing the control relay CR connected in series with'the secondary coil S in a circuit verysimilar to that for energizing the control relay GR in Fig. 2.- This circuit may be traced as follows :-beginning at the terminal 5B,, wire 80 also connected to; one

terminal of the check relay CkR, wire 86,

front contact 87 of the check relay CkR, wire 88, front'contact21 of the repeater relay RR,

wires 89 and 90, front contact 33 of the control relay CR, wires 91 and 92, secondary coil S, wire 93, winding of the control relay CR, wire 94 leading to theother terminal of the check relay CkR. The repeater relay BB is energized through the following circuit beginning at the terminal B, wires 80 and 86, front contact 87 of the. check relay CkR, wire 88, front contact 21 of the repeater relay PB, wire 100, normally closed slow released contact 43 of the acknowledging device Ack,

RR, wires 89 and 90, front contact 33 of the wire 101, winding of the device EPV, wire 102 to a common return wire 0 connected to the other terminal of such source.

Operation (Fig. l).-In considering the operation of the system shown in Fig. 4, let us first consider a train equipped with the car-carried apparatus shown in this figure assuming it to be in its normal condition as 'illustrated and passing by a trackway device which is in its active stoppin condition, that is, having its coil 12 open-clrcuitedg As the train passes by this trackway inductor T a potential is induced in the secondary coil S of the car element L which is in a direction to oppose a potential dropv due to the current flowing in the winding of the check relay OkR and is of a magnitude sulficient to deenergize the control relay OR for reasons given in connection with the system shown in Fig. 2. With the control rela CR once dropped its energizin circuit is roken by reason of-opening 0 its stick contact 33, whereby the repeater relay" HR is also deenergized. With the repeaterrelay BB in its de-energized position, the stick circuit for the control relay OR is broken at another point,so that, even if the engineer depresses the acknowledging button Ack he can not againpick u the controlrelay CR. This means that ac nowledgement, as more clearly .pointed out hereinafter, must take place during the reception of a control influence, that .is, must anticipate and'nrecede and not fol- -EPV is broken'at front contacts 61 of this repeater relay RR, whereby the train is brought to a stop in a manner as already explained in connection with the embodiment of the invention shown in Fig. 2 of the drawings. It should, however, be noted that the primary coil P has not been de-energized; this coil P still receives energy through the winding of the check relay CkR. In other words, the device EPV has been automatically operated without breaking the heavy energizing current for the primary coil P, so that, the current actually interrupted by the repeater relay RR is only that required for energizing the device EPV and the'discharge resistance 73 is not required.

On the other hand, the integrity of the circuit including the primary coil P is checked by the check relay CkR, so that, interruption of this circuit or depreciation of the source of energy for energizing it is automatically de-.

tected by dropping of this relay; further, weakening of the field of flux produced by the primary coil P which would tend to weaken the impulse transmitted to the control relay GR is compensated for by a corresponding reduction of the potential applied to this control relay, this because the potential impressed upon the control relay GR is directly proportional to the amount of current flowing in the primary coil P, so that a correspondingly weaker impulse is necessary to de-energize the control relay CR when the current for energizing the primary coil is reduced.

After the train has been brought to a stop by reason of the automatic brake application for reasons just given, the'train may again proceed if the engineer alights to the ground and depresses the reset push button PB. which is mounted in a casing as indicated by the dotted rectangle and is only accessible from the ground. Depression of this push button PB closes a pick-up circuit for the control relay CR including the potential drop due to the current flowing in the winding of the check relay CkR, which may .be traced as follows :-beginning at the wire 86 connected to one side of the check relay CkR, front contact 87 of this check relay CkR, wire 103, normally open contact 51 of the push button PB, wires 104-, 105 and 92, secondary coil S, wire 93, winding of the control relay .CR, wire 94, to the other terminal of the check relay CR. Completion of this pick-up circuit causes the control relay CR to assume its energized position and again complete its normally closed stick circuit, because the potential impressed across relay CkR is also impressed across the circuit portion including the coil S and the relay CR in series. As soon as this occurs and the engineer continues to depress the push button PB an energizing circuit for picking up the repeater relay RR is closed which is the same as the pick-up circuitfor the control relay CR just traced up to wire 105 from whence it comprises wire 91, front contact 33 of the control relay CR, Wires 95 and 96, Winding of the repeater relay RR, wire 97 to common return wire C. With the repeater relay RR, again picked up and stuck up through its stick contact 21 the energizing circuit for the device EPV heretofore traced is again closed, whereupon the brakes may be released by the engineer and the train may again proceed until it is restricted at another control point. It shouldbe noted that whilethe push button PB is depressed to pick up the control relay CR, and in turn the repeater relay RR, the energizing circuit for the device EPV is broken at another point, namely at the normally closed contact 41 of the push button PB. This breaking of the circuit for the device EPV is provided for, so that, the engineer can not permanently tie. down or otherwise fasten t-he push button PB in its active position, and thereby defeat. the purpose of the train control system by providing a continuously etlective reset.

In other words, the .push button PB must be returned to normal before. the device EPV is a ain ener ized and the brakes can'be released.

Let us now assume that the train in question with its car-carried devices in their normal condition passes by an active track-element 'l, and that the engineer is vigilant and inanifests such vigilance by depressing the acknowledging push button Ack. With the acknowledging push button Ack depressed, two shunting contacts 58 and 03 are closed. The contact 58 through a partial circuit rcadily traced in the drawing shunts the righthand side of front contact 33 of the control relay CR for preventing the repeater relay RR dropping in response to momentary dropping of the control relayCR, and the contact 63 through a partial circuit readily traced shunts the lefthand portionof contact-33 of the control relay CR, so that this control relay CR is connected non-stick so long as the acknowledging push button Ack is depressed. If now the car element L passes over the track element '1 in its active condition while the acknowledging push button Ack is depressed by the enginecrthe control relay GR is momentarily (lo-energized. This momentary de-energization of the control relay has no effect upon the repeater relay RR, because this repeater relay RR is held up by the acknowledging push button Ack, by the depression of which the engineer has avoided an automatic brake application. In this connection. it should be noted that the time during which an acknowledgment may be made must be limited by reason of opening of normally closed slow releasing contacts 43 of the acknowledging push button Ack for reasons given in connection with Fig.

The functioning of the car-carried apparatus in the modification shown in Fig. 4 when passing over an inactive closed circuited trackway inductor is the same as that of the system heretofore described, that is, insulticient voltage is induced in the secondary coil S to effect the control relay CR and therefore no operation results for reasons already mentioned.

' Structure and operation (Fp'g. )'.In certain classes of railway trans 1t is considered expedient in intermittent train control systerns of the type shown in Fig. 2 to require sible for the engineer to enter caution or danger territory without the cooperation and the aid of the fireman, because only one of two acknowledging devices are operable at one time by the same man.

As heretofore mentioned, it is necessary for the engineer or fireman to alight from the,

train each time that an automatic brake application occurs in order to again release the brakes after coming to a stop. This reset push button PB is preferably located along the side of the tender or beneath the same and 1 is accessible only by a man walking along the side of the train. In practice, it has been experienced that at certain places, and especially on high, trestles and bridges, it is possible to alight from one side of the engine only, and in accordance with the present invention it is proposed-to provide a reset push button on each side of the tender so that if it is only possible to alight from one side of the train, a reset push button is still accessible.

- The car-carried apparatus shown in Fig.

5 is intended to provide this feature and is identical to that shown in Fig. 2 except that two acknowledging buttons Ack and Ack are used instead of'one as shown in Fig. 2. It should be noted'that the two acknowledging push buttons shown have all of'their normally open corresponding contacts connected in series, this beingdone so that both of these acknowledging push buttons must be depressed before such acknowledgement is ef- 1 fective whereas in the case of the push but-v tons PB'the normally open corresponding contacts are connected in multiple so that the operation of either of these push buttons produces the desired effect. Further, it

should be noted that the normally closed contacts of both the acknowledging and reset push buttons are connected in series so that all of these devices are protected against misuse as more clearly heretofore set forth.-

The arrangement shown in'Fig. 5 thus requires the cooperation of theengineer and fireman before an activecontrol point may be passed without the imposition of an automatic brake application, so that, the engineer can not enter dangerous territory without the consent and knowledge of the fireman, which in turn will cause the fireman to observe whether the engineer is-properly controlling the train and whether he is capable of so controlling it.- Also, in this embodiment of the invention, a properly protected reset device has been provided to be accessible by alighting from either-side of the engine, this in or-.

der to permit a reset device to be operated regardless of the direction of movement of the train over bridges, viaducts, and the like even though such bridges and viaducts have provision for walking along one side of the train only.

Having thus'show'n and described several specific embodiments of the invention, and having described themrather specifically, it is desired to be understood that this has been done for the purpose of disclosing the inven tion rather than illustrating its scope or the exact circuit arrangements preferably employed in ractice, and that various clg nges and modi ications may be made to adapt the invention to the various systems encountered in practice without departing from the spirit of the invention or the idea of means underlying the same.

What I claim is '1. In an automatic train control system;

the combination of an electro-responsive de vice which if in its retracted position restricts the movement of the trainya source of energy; a ballast lamp; a circuit including said device, said source and said lamp in series; and an inductive influence communicating means located in inductive relation with the trackway for changing the flow of current in said circuit.

'2. A train control system comprising, an inductive influence'communicating device for communicating'influences from the trackway to the vehicle inductively, a source of current;

a circuit including said device and said source in series, and means included in said circuit.

for compensating for changes of flow of cur rent in said circuit due to changes in the potential of said source orchanges in temperature.

3. Oar-carried apparatus for automatic H train control systems comprising; an electroresponsive device which if de-energized restricts the movement of the train, a source of energy;a ballastldevice; and a circuit including said electro-responsive device, said source and saidballast device in series; said ballast device being-constructed to compensate by changing the voltage impressed upon said electro-responsive device for changes in the flow of current in said c1rcuit due'to changes in temperature and battery voltage.

4. Car-carried apparatus for automatic train control. systems comprising, an in- 5. Car-ca rried apparatus for automatic train control systems comprising, an infiuence receiving car element consisting of an inverted U-shaped core of magnetic material having a primary flux producing coiling in series said primary coil, a source of.

current and said current regulating device, said electro-responsive device having connected in multiple therewith said control relay and said secondary coil connected in series, whereby said regulating device directly regulates the flow of current in said primary coil and in said control relay, and a changein the flow of current in said primary coil changes the potential applied to said control relay.

6. An automatic train control system comprising, an inductive influence communicating devlce; a source of current; a self-adjust- .ing current regulating device; and a circuit including said influence communicating device, said regulating device and said source of current in series; said regulating device consisting of a resistance unit having a high temperature co-efiicient of resistance housed so that heat is not readily radiated there-' from.

7. In an automatic train control system, the combination of a train retarding device, an electro-responsive means, a circuit for energizing said retarding device including a front contact of said electro-respon'sive means, a circuit for energizing said electroresponsive means including a front contact of said retarding device, and a ballast lamp in a clrcuit portlon common to both of said circuits.

8. Car-carried apparatus for automatic train control systems comprising, a control relay, a repeater relay, a train retarding device, a push button, a circuit for energizing said train retarding device including a front contact of said repeater relay, a stick circuit for energizing said control relay includinga front contact of said train retarding device, a circuit for energizing said repeater relay including a front contact ofsaid control relay,ana a pick up circuit for said control relay including a back contact of said repeater relay and a normally open contact of said push button, and means for independently energizin said train retarding device when said push utton is depressed.

9. Car-carried apparatus for automatic train control systems comprising, a control relay, a repeater relay, a train retarding device. a circuit for energizing said train re tarding device includin afront contact of said repeater relay, a stick circuit for energizing said control relay including a front contact of said train retarding device, a circuit for energizing said repeater relay including a front contact of said control relay, and means which? if depressed independently energizes said train retarding device and closes a pick up circuit for said control relay while, said repeater relay is in its deenergized position.

10. Car-carried apparatus for automatic train control systems comprising, a control relay, a repeater relay, a train retarding device, a circuit for energizing said train retarding device includin a front contact of said repeater relay, a stud: circuit for energizing said control relay including a front contact of said train retarding device, a circuit for energizing said repeater relay including a'front contact of said control relay, and means efiective if depressed for independently energizing said train retarding device through a circuit including an audible signal and for completing a pick up circuit for said control relay while said repeater relay is tie-energized.

11. Car-carried apparatus for automatic train control systems comprising, an electropneumatic valve which if de-e-nergized effects venting of the brake pipe of the usual air brake system, inductive influence communicating means consisting of a secondary coil and a primary coil energized by a circuit having an external resistance therein, a control relay, a repeater'relay, a circuit for energizing'said repeater relay including a source of energy and front contacts of said control relay and said repeater relay connected in series, a circuit forenergizing said control relay including said secondary coil and the front c0ntacts of said control relay and said repeater relay in series and bridged across said resistance, a circuit'controlled by said repeater relay for energizing saidelectro-pneumatic valve, and manually operable means for bridging the front contacts of said control relay and said repeater relay.

v12. Car-carried apparatus for automatic train control systems comprising, an influence receiving car element consisting of an. inverted U-shaped core of magnetic material having a primary flux producing coil on one leg and a secondary influence receiving coil on the other leg, a circuit for energizing said primary coil including a source of energy and a self-adjusting current regulating device in series, and means effective to apply the brakes of the trainif said circuit is broken.

13. In an automatic train control system,

electrically operable brake control mechanism' of the type which if momentarily de-energized will remain de-energized until restored by some other means, and manually operable devices accessible only from the ground for restoring said brake control mechanism, said manually operated devices each alone being operable reset devices located on opposite sides of the train and located so as to be accessible only by-a man standing on the ground each comprising, a normally open contact which if closed completes a pick-up circuit for said brake applylng means and having a normally closed contact which if broken effects an automatic brake application.

15. Gar-carried apparatus for automatic train control systems comprising, an influence receiving car element consisting of an inverted U-shaped core of magnetic material having a primary flux producing coil on one leg and a secondary influence receiving coil on the other leg, a circuit for energizing said primary coil including a source of energy, an

' electro-responsive device and a self-adjusting current regulating device in series, and a circuit for energizing said secondary influence receiving coil in which the current isderived from the voltage drop over said electro-responsive device.

l6. Car-carried apparatus for automatic train control systems of the intermittent inductive type; the combination with an inductive influence communicating means including an influence receiving coil; a normally energized control stick relay, repeater stick relay and train retarding stick relay; an energizing circuit for said influence receiving coil including the winding of said control relay in series therewith and including contacts of said control relay, contacts of a repeater relay and contacts of said train retarding relay in series all of which contacts are closed when said respective relays are energized; an energizing stick circuit for said repeater including normally closed contacts of said control relay and normally closed contacts of said train retardingrelay, and an energizing circuit for said train retarding relay including its own normally closed contact and a normally closed contact of said repeater. relay.

17. A train control system comprising, an inductive influence communicating device for communicating influence from the trackway to the vehicle inductively, and includinga primary flux producing and a secondary influence receiving coil; a unit of comparatively low electrical resistance connected in series with said flux producing coil; a control relay having a front stick contact connected in series with its winding; a source of current; a

circuit for energizing said flux producing coil including, said unit, said source of current and means for compensating for flow of current in said circuit due to changes in the potential of said source; and a circuit for energizing said control relay including in series said receiving coil, said unit,-sa1d control relay and its front contact all in series and receiving its energy from the potential drop across said low resistance, unit.

In testimony whereof I aflix my signature.

' CHARLES S, BUSHNELL. 

